1. Field of the Invention
The present invention relates generally to antennas and, more particularly, to a directivity enhancer for an antenna.
2. Description of the Related Art
We live in a networked world. It is not uncommon for a house to have multiple computers, all networked together. In addition to computers, tremendous numbers of electronic devices are deployed all over the world everyday. They can be sensors for collecting information, actuators for providing certain mechanical manipulations, or communication devices, such as cellular phones. Increasingly, electronic devices are also networked together for specific applications. The following descriptions are focused on networked computers. However, similar challenges exist for other electronic devices.
Three common mechanisms used to network computers in an indoor environment are Ethernet, Phone Line (HomePNA) and wireless network. Examples of wireless networks are WiFi and 802.11b. Sometimes these networks are referred to as wireless Ethernet. At present, Ethernet is more popular than the other two approaches for both home and business.
Ethernet networks are relatively stable, and the network speed is typically not prone to interference. In an Ethernet network, special cables running from each computer are connected to a central Ethernet hub or switch. It is quite cumbersome to run cables to connect the computers together, particularly when the computers are far apart.
Phone Line Networks, also known as HomePNA networks, use existing phone lines to wire computers together. The networks allow the same phone-line wires in a house to operate the network. They do not interfere with the normal operation of phone lines for voice, fax or modem use. However, the network requires phone lines to physically connect to the different computers.
Wireless networks are similar to regular Ethernet, except totally wireless networks do not require wires for connections. One common type of wireless networks is the WiFi network, championed by the WiFi Alliance. The WiFi Alliance is a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on the IEEE 802.11 specification.
At present, the more common 802.11 networks are the 802.11a and 802.11b networks. The 802.11b network operates around 2.4 GHz and can send data up to 11 Mbps. And, the 802.11a network operates around 5 GHz and sends data up to 54 Mbps. As a result, 802.11a provides higher bandwidth. On the other hand, the higher operating frequency typically equates to shorter range. For example, the range of 802.11a systems can be up to 60 feet, which is less than the up-to 300 feet operating range of the 802.11b systems.
Computers equipped with wireless cards or embedded wireless antennas can communicate without the need for any additional hardware. However, many homes still use wires to connect computers to the Internet based on a wired Ethernet arrangement. One way to bridge a wired computer to wireless computers is through an access point. One computer in the house can be connected to the Internet through a wire (e.g., coupled to phone or network jack). That computer is also connected through a wire (e.g., cord) to an access point. The access point has an antenna that wirelessly couples to other computers in the house. In other words, the access point can bridge or route wireless traffic to a wired Ethernet network.
Like a cordless phone, once a portable computer is connected to a wireless network, the computer is free to roam a house. Theoretically, you should be able to carry the computer around the house, without losing connections to the network. You should be able to surf the Web sitting in the living room, while watching TV; in the toilet, while brushing your teeth; or on a swing in the backyard. Obviously, the flexibility of wireless networks without tethered connections has its attractions.
However, wireless networks are not without challenges. For example, wireless Ethernet networks operate around 2.4 GHz range. It is the frequency band that is used for many other applications, including satellites, baby monitors, garage-door openers, microwave ovens, Bluetooth networks, and high-end wireless phones. Such a wide range of applications creates interference and increases the noise level on wireless networks.
More importantly, wireless networks operate on radio frequencies. Heavy walls, metal meshes sandwiched inside walls and large metal objects, such as bookshelves and file cabinets, all interfere with radio signals. It is not uncommon for a portable computer to have a relatively stable connection if it is close to an access point, but have problematic intermittent connection if it is used in a different room than the room having the access point. This can cause a lot of frustration to the user of the portable computer who is attempting to use the wireless network.
It should be apparent from the foregoing that there is still a need to improve connections over wireless networks.